CN110833427A

CN110833427A - Grating imaging system and scanning method thereof

Info

Publication number: CN110833427A
Application number: CN201911201422.4A
Authority: CN
Inventors: 张丽; 陈志强; 高河伟; 李新斌; 邢宇翔
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2020-02-25
Anticipated expiration: 2039-11-29
Also published as: CN110833427B

Abstract

The invention discloses a grating imaging system, wherein the system comprises: a source grating (G0) for converting incoherent light emitted by the light source into coherent light; a first grating (G1) formed by splicing a plurality of first grating units and used for acquiring a first image after the coherent light passes through the first grating (G1); and a second grating (G2) formed by splicing a plurality of second grating units, and used for operating the first imaging to obtain a second imaging; the imaging irradiation position is arranged between the first grating (G1) and the second grating (G2), and the source grating (G0), the first grating (G1) and the second grating (G2) form a light path to form a system. The system maintains good image quality, reduces the whole scanning time to a level close to that of a clinical X-ray chest film, and simultaneously well controls the radiation dose; in summary, the large-field grating imaging system has the advantages and characteristics of large imaging field of view, high scanning speed, low radiation dose and the like.

Description

Grating imaging system and scanning method thereof

Technical Field

The invention relates to the technical field of optical imaging, in particular to a grating imaging system and a scanning method thereof.

Background

The X-ray grating phase contrast imaging technology can realize local structure resolution on a micron or submicron scale, and is a good supplement to the traditional X-ray imaging technology. The technology can simultaneously extract three kinds of information of absorption, phase contrast and dark field images, is suitable for distinguishing low atomic number and low density substances, and is particularly suitable for biological soft tissue structures including mammary glands. In order to obtain better image quality, grating imaging techniques typically acquire data in a phase-stepping manner. The method refers to that one of the gratings is subjected to equidistant displacement in one or more periods along the direction vertical to the grating lines of the grating, so that displacement curves before and after the object is placed are obtained.

The grating imaging system is mainly used for imaging research of small samples or small animals, the imaging field size is about a few centimeters, the energy of an X-ray beam is low (15-60kVp), the corresponding grating group size is small, the depth-to-width ratio (the ratio of the grating gold plating thickness to the grating slit width) of the grating is low, and the current grating manufacturing process is sufficient. However, to advance the raster imaging technique to clinical practice, a larger imaging field of view (up to 20-50cm) and higher X-beam energies (up to 60-120kVp) are required. The larger imaging field of view also means a larger size grating group, and the current grating manufacturing process cannot be finished at one time. Similarly, for the traditional grating imaging mode, the mode that the measured object moves relative to the grating is generally adopted for scanning, and the scanning process is relatively complex; in addition, the traditional phase stepping scanning is time-consuming, and the radiation dose is higher, so that the radiation dose is harmful to the measured object. Therefore, in order to reduce the total scanning time and the radiation dose, and ensure the imaging quality, the imaging system and the scanning mode need to be optimized and improved.

Disclosure of Invention

Technical problem to be solved

The invention provides a novel large-field grating imaging system and a scanning method thereof, which comprise a system structure and a scanning imaging mode, thereby realizing large-field imaging which meets the clinical requirement, quickly and effectively realizing scanning imaging, avoiding redundant imaging time and radiation dose in the traditional grating imaging process and simultaneously ensuring good enough image quality.

(II) technical scheme

One aspect of the present invention proposes a grating imaging system, wherein the system comprises a source grating G0, a first grating G1 and a second grating G2 arranged in sequence along an optical path, wherein: the source grating G0G0 is used for converting incoherent light emitted by the light source into coherent light; the first grating G1 is formed by splicing a plurality of first grating units and is used for acquiring a first image after coherent light passes through the first grating G1; the second grating G2 is formed by splicing a plurality of second grating units and is used for operating the first imaging to obtain a second imaging; wherein, an imaging irradiation position is arranged between the first grating G1 and the second grating G2.

Optionally, when the plurality of first grating units and the plurality of second grating units are respectively spliced along the one-dimensional direction, the first grating G1 and the second grating G2 satisfy the following formula:

wherein, w₁Is the width, h, of the first grating G1₁The height of the first grating G1; w is a₂Is the width, h, of the second grating G2₂Is the height of the second grating G2; l is a first pitch between the source grating G0 and the first grating G1, d is a second pitch between the first grating G1 and the second grating G2.

Optionally, a second pitch d between the first grating G1 and the second grating G2 satisfies the following formula:

where l is the first separation between the source grating G0 and the first grating G1; p is a radical of₀、p₁、p₂Respectively a source grating G0 and a first gratingG1 and a second grating G2, lambda is the X-ray wavelength, n is a constant, n is an odd number when the first grating G1 is a phase grating, n is an even number when the first grating G1 is an absorption grating, η is another constant related to the grating type, η is 1 when the first grating G1 is a pi/2 phase grating or an absorption grating, and the first grating G1 is 2 when the first grating G1 is a pi phase grating.

Optionally, when the first grating is an absorption grating, the second distance d between the first grating and the second grating satisfies the following formula:

where l is the first separation between the source grating G0 and the first grating G1; p0, p1, p2 are the periods of the source grating G0, the first grating G1 and the second grating G2, respectively.

Optionally, when the first grating unit is horizontal in the grid direction, a plurality of first grating units are spliced in the horizontal direction to form a first grating G1, and a plurality of second grating units are spliced in the horizontal direction to form a second grating G2; or when the grid direction of the first grating units is vertical, the plurality of first grating units are spliced along the vertical direction to form the first grating G1, and the plurality of second grating units are spliced along the vertical direction to form the second grating G2.

Optionally, when the first grating unit is horizontal in the grid direction, a plurality of first grating units are spliced in the vertical direction to form a first grating G1, and a plurality of second grating units are spliced in the vertical direction to form a second grating G2; or when the grid direction of the first grating units is vertical, the plurality of first grating units are spliced along the horizontal direction to form the first grating G1, and the plurality of second grating units are spliced along the horizontal direction to form the second grating G2.

Optionally, the system further comprises a detector having a pixel size larger than the period of the first grating G1 for viewing a second image of the second grating G2.

Optionally, a metal plating layer is disposed on the surface of the first grating G1, and a material of the metal layer is selected to be a heavy element metal, including: gold, silver, tungsten or lead.

Optionally, the first grating G1 and the second grating G2 are formed by splicing a plurality of first grating units and a plurality of second grating units in a laminated manner along a one-dimensional direction, and the first grating G1 and the second grating G2 are two-dimensional plane gratings.

Alternatively, when the stack is a double stack, the grid shape of the two-dimensional planar first grating G1 is formed by the grating periods p of the first and second stacked grating elements of the first grating element₁₁、p₁₂And its grid direction; and the grid shape of the two-dimensional planar second grating G2 is composed of the grating periods p of the third and fourth stacked grating units of the second grating unit₂₁、p₂₂And its grid direction.

In another aspect of the present invention, a raster imaging scanning method applied to the above raster imaging system is provided, where the method includes: the control system moves along the vertical direction to scan the imaging irradiation position between the first grating G1 and the second grating G2; exposing the imaging irradiation position at a specific scanning height; and extracting the exposed data information to acquire imaging.

Optionally, exposing the imaging illumination location at a particular scan height comprises: when the system reaches a certain scan height, the second grating G2 is controlled to perform a phase step scan in the horizontal direction to reach a certain scan step length, the imaging exposure position is exposed.

Optionally, exposing the imaging illumination location at a particular scan height comprises: before the system reaches a specific scanning height, the second grating G2 is controlled to perform phase stepping scanning in the horizontal direction to reach a specific scanning step; and exposing the imaging exposure site after the system reaches a particular scan height.

Optionally, exposing the imaging illumination location at a particular scan height comprises: completing the first exposure at a first specific scanning height, and completing the second exposure at a second specific scanning height; wherein the height of the nth and n +1 th first grating elements of the first grating G1Difference h_n,n+1The following formula is satisfied:

h_n,n+1＝m·Δh

wherein m is a positive integer, Δ h is a third distance between the first specific scanning height and the second specific scanning height; height difference h between nth and n +1 th second grating units of second grating G2_n,n+1The following formula is satisfied:

where m is a positive integer, l is a first spacing between the source grating G0 and the first grating G1, p₂N is the number of phase steps of the second grating G2 for the period of the second grating G2.

(III) advantageous effects

One aspect of the present invention provides a novel large field-of-view grating imaging system. The system can manufacture large-area gratings meeting the requirements of large-field imaging and the like in a splicing mode, can realize large-area imaging field matched with clinical medicine, and can realize scanning imaging of a large-size sample and even a human body; in addition, the depth-to-width ratio of the grating is improved to be suitable for the X-ray with higher energy, and the imaging irradiation position is arranged between the first grating G1 and the second grating G2 to reduce the radiation dose of the object and reduce the generation of ineffective X-ray; practical experimental data show that the system maintains good image quality, the whole scanning time is reduced to a level close to that of a clinical X-ray chest film, and meanwhile, the radiation dose is well controlled; in summary, the large-field grating imaging system has the advantages and characteristics of large imaging field of view, high scanning speed, low radiation dose and the like.

The invention provides a grating imaging scanning method on the other hand, which is applicable to various scanning modes, can realize a fast scanning mode to improve the scanning efficiency, and combines the triggering type exposure-acquisition control to avoid the generation of invalid X rays and reduce the radiation dose of the system as much as possible; in addition, the imaging irradiation position is placed between the first grating G1 and the second grating G2 to reduce the radiation dose of the object and reduce the generation of invalid X-rays, and meanwhile, the mode of moving scanning of the control system to replace the moving scanning of the imaging irradiation position is adopted, so that the scanning imaging time is further shortened, the imaging field of view is improved, the method can also be suitable for scanning imaging of a detected object with a larger body size and a higher thickness, the radiation dose is reduced, the overall scanning efficiency is improved, and the step of the grating imaging technology towards clinical application is promoted.

Drawings

FIG. 1 is a schematic diagram of a grating imaging system according to an embodiment of the present invention;

FIG. 2A is a diagram illustrating a first grating unit according to an embodiment of the present invention;

FIG. 2B is a diagram illustrating a second grating unit according to an embodiment of the present invention;

FIG. 3A is a schematic illustration of a mosaic of a raster imaging system in an embodiment of the present invention;

FIG. 3B is another schematic illustration of a mosaic of a raster imaging system in an embodiment of the invention;

FIG. 4 is a schematic diagram of a two-dimensional planar grating patch for a grating imaging system according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating a raster imaging scanning method according to an embodiment of the present invention;

FIG. 6A is a top view of a component of a grating imaging system in accordance with an embodiment of the present invention;

FIG. 6B is a side view of a grating imaging system according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a raster imaging system employing a fast scan method according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of the components of a grating imaging system in one embodiment of the present invention;

FIG. 9 is a schematic diagram of the first grating G1 according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of the components of a grating imaging system in accordance with an embodiment of the present invention;

FIG. 11 is a schematic diagram of a cross-spliced large area grating according to an embodiment of the present invention;

FIG. 12 is a flow chart illustrating a raster imaging scanning method according to an embodiment of the present invention;

FIG. 13 shows absorption, phase contrast, and dark field images from grating imaging experiments in accordance with an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.

Example 1:

one aspect of the present invention proposes a grating imaging system, as shown in fig. 1, wherein the system comprises a source grating G0, a first grating G1 and a second grating G2 arranged in sequence along an optical path, wherein: the source grating G0 is used for converting incoherent light emitted by the light source into coherent light, and the first grating G1 formed by splicing a plurality of first grating units is used for acquiring a first image after the coherent light passes through the first grating G1; the second grating G2 is formed by splicing a plurality of second grating units and is used for operating the first imaging to obtain a second imaging; wherein, an imaging irradiation position is arranged between the first grating G1 and the second grating G2. In other words, the source grating G0, the first grating G1, and the second grating G2 form a light path to form a system.

Specifically, as an embodiment of the present invention, the light source is an X-ray light source, the X-ray beam emitted by the light source generates a series of partially coherent linear light sources through a source grating G0, and the source grating G0 serves as a source grating, so that the system can be applied to coherent light sources or incoherent light sources; the first grating G1 is a phase grating or an absorption grating, the second grating G2 is an analysis grating, and the X-ray generates self-imaging of the first grating G1 at a certain distance after passing through the first grating G1, namely first imaging; when an object to be irradiated is arranged on an imaging irradiation position arranged between the first grating G1 and the second grating G2, the second imaging is the imaging of the X-ray camera irradiated on the object through the first grating G1 and then through the second grating G2, and the imaging is observed on a detector.

In the grating manufacturing process, the first grating G1 and the second grating G2 cannot be directly manufactured at one time, and grating sub-blocks, that is, grating units, need to be manufactured first. The source grating G0 is very close to the X-ray source, so the size requirement is low, and the processing can be finished at one time; the first grating G1 and the second grating G2 have large sizes and need to be spliced by 2 or more grating sub-blocks, that is, the first grating G1 formed by splicing a plurality of first grating units and the second grating G2 formed by splicing a plurality of second grating units obtain a large-area grating meeting requirements in a splicing manner, wherein the sizes, the grating periods, the grating directions and the like of the first grating units and the second grating units can be respectively inconsistent. In addition, regarding the splicing mode, a certain gap can be formed between the adjacent grating units so as to meet various imaging requirements.

In the grating imaging system in the art, in order to obtain a clearer imaging effect with a smaller imaging magnification, the imaging illumination position is generally arranged between the source grating G0 and the first grating G1. However, such a design would result in about 1/4X-ray total amount received by the detector, which is the total amount of X-ray penetrating the object at the imaging irradiation position, and at the same image quality level, the absorption dose of the detected object would be about 4 times that of the conventional X-ray attenuation imaging (such as X-ray chest radiography imaging, etc.), which is difficult to achieve the clinical radiation dose standard. In order to reduce the radiation dose of the system, as an embodiment of the present invention, the imaging exposure position is placed between the first grating G1 and the second grating G2, so as to reduce the radiation dose of the object and reduce the generation of ineffective X-rays, as shown in fig. 1. Compared with the system structure design that an object is placed between the source grating G0 and the first grating G1, the radiation dose of the system structure design is reduced by about half, and the system structure design optimization is easier to achieve clinical standards.

Correspondingly, after the detected object is placed on the imaging illumination position of the imaging system, the corresponding grating stripe on the detector will generate local distortion, the detected object is scanned in a phase stepping manner along the direction perpendicular to the grating grid (the second grating G2 can be optionally moved, the total scanning step length is usually one grating period, and optionally, the stepping length of each time is consistent), so that a scanning detection background displacement curve (without placing the object) and an object displacement curve (with placing the object) of the imaging illumination position are obtained, and then three kinds of image information of absorption, phase contrast and dark field are simultaneously obtained by utilizing information extraction algorithms such as CMA and SAXS.

As an embodiment of the present invention, when the plurality of first grating units and the plurality of second grating units are respectively spliced along the one-dimensional direction, the first grating G1 and the second grating G2 satisfy the following formula (1):

Specifically, as shown in fig. 2A and 2B, in consideration of the fact that the difficulty of grating stitching is high in practice, it may be considered to perform the stitching in a one-dimensional direction at present, that is, in a case where the second grating G2 is kept to be capable of effectively obtaining the image of the first grating G1, the stitching directions of the plurality of first grating units and the stitching direction of the second grating units are the same, for example, when the stitching direction of the plurality of first grating units is a positive x-axis direction, the stitching direction of the plurality of second grating units may also be selected as a positive x-axis direction or a negative x-axis direction. The central connecting line of the source grating G0, the first grating G1, and the second grating G2 may constitute the grating imaging light path of the present system. In addition, the first grating G1 and the second grating G2 shown in fig. 2A and 2B can also be used as the first grating unit and the second grating unit, that is, when the first grating G1 and the second grating G2 are respectively composed of only 1 first grating unit and only 1 second grating unit, the above formula (1) is also satisfied.

As an embodiment of the present invention, the second pitch d between the first grating G1 and the second grating G2 satisfies the following formula (2):

formula (3):

and formula (4):

where l is the first separation between the source grating G0 and the first grating G1; p is a radical of₀、p₁、p₂The periods of the source grating G0, the first grating G1 and the second grating G2 are respectively, lambda is the X-ray wavelength, n is a constant, n is an odd number when the first grating G1 is a phase grating, n is an even number when the first grating G1 is an absorption grating, η is another constant related to the grating type, η is 1 when the first grating G1 is a pi/2 phase grating or an absorption grating, and the first grating G1 is 2 when the first grating G1 is a pi phase grating.

In addition, the grating G1 can be selected as a phase grating or an absorption grating, the second grating G2 can be selected as an analysis grating, and the second grating G2 is placed at a specific distance behind the first grating G1, wherein the specific distance satisfies the above formulas (2), (3) and (4) related to the period of each component grating, the wavelength of incident X-rays and the characteristic of the grating, for example, the value of n or η is related to the type of the grating.

As an embodiment of the present invention, in order to make the grating imaging technology more suitable for the incoherent X-ray source, the moire fringes generated by the superposition of the projection of the first grating G1 and the second grating G2 can be selected to realize imaging, and such a system is called as "geometric projection system". in this system, when the absorption grating is selected, i.e. n is an even number, η is 1, the above equations (3), (4) can be transformed accordingly, i.e. the system parameters thereof need, i.e. the second distance d between the first grating G1 and the second grating G2 can also satisfy equation (5):

formula (6):

where l is the first separation between the source grating G0 and the first grating G1; p is a radical of₀、p₁、p₂The periods of the source grating G0, the first grating G1, and the second grating G2, respectively.

Comparing the above equation (2), (3) or (4) system with the geometric projection system, it can be seen that the first grating G1 usually employs a phase grating, a specific system X-ray energy is required to be designed to correspond to the phase grating to realize modulation, and the second grating G2 must be placed at a specific distance behind the first grating G1; the latter relaxes the system parameter requirements, the system X-ray energy and the position of the second grating G2 are not limited, i.e. the distance between the first grating G1 and the second grating G2 does not need to be fixed, which is more suitable for practical applications, for example, a larger object to be detected is arranged at the imaging irradiation position between the first grating G1 and the second grating G2. As an embodiment of the present invention, the large-field grating imaging system preferably adopts the design of the above-mentioned geometric projection system.

As an embodiment of the present invention, when the first grating unit is horizontal in the grid direction, a plurality of first grating units are spliced in the horizontal direction to form a first grating G1, and a plurality of second grating units are spliced in the horizontal direction to form a second grating G2; or when the grid direction of the first grating units is vertical, the plurality of first grating units are spliced along the vertical direction to form the first grating G1, and the plurality of second grating units are spliced along the vertical direction to form the second grating G2.

As an embodiment of the present invention, when the first grating unit is horizontal in the grid direction, a plurality of first grating units are spliced in the vertical direction to form a first grating G1, and a plurality of second grating units are spliced in the vertical direction to form a second grating G2; or when the grid direction of the first grating units is vertical, the plurality of first grating units are spliced along the horizontal direction to form the first grating G1, and the plurality of second grating units are spliced along the horizontal direction to form the second grating G2.

Specifically, in the case where the central connecting line of the second grating G2 and the first grating G1 coincides with the optical path, the splicing direction of the selectable second grating unit and the splicing direction of the first grating unit are kept coincident. For example, when the splicing direction of the first grating units is a positive x-axis direction, the splicing direction of the second grating units can also be selected to be a positive x-axis direction or a negative x-axis direction, as shown in fig. 3A or fig. 3B. The grid direction of the first grating unit and the grid direction and the splicing direction of the second grating unit may be unrelated, while the grid directions of all spliced first grating units of the selectable first grating G1 are consistent, and similarly, the grid directions of all spliced second grating units of the selectable second grating G2 are consistent. Specifically, as shown in fig. 3A or 3B, the first grating units of the first grating G1 have a horizontal grating direction (or the first grating units have a vertical grating direction), 2 or more than 2 first grating units are spliced along the x-axis direction, the grating direction of the corresponding second grating unit of the second grating G2 is irrelevant, and the splicing direction is specifically either positive or negative along the x-axis when the axes are opposite. Accordingly, as a preferred aspect of the present invention, the grid directions of the optional source grating G0, the first grating G1 and the second grating G2 are kept consistent, i.e. the grid directions of the first grating unit and the second grating unit are consistent, e.g. when the grid direction of the first grating unit is horizontal, the grid direction of the second grating unit is also kept horizontal.

As an embodiment of the invention, the system further includes a detector having a pixel size larger than the period of the first grating G1 for viewing a second image of the second grating G2. Specifically, as shown in fig. 1, the X-ray passing through the first grating G1 produces a self-image of the grating over a distance, i.e., a first image; when the pixel size of the detector T is far larger than the period P1 of the first grating G1, the second grating G2 is adopted to realize the amplification of the self-imaging of the first grating G1 to obtain a second imaging, and the second imaging is observed through the detector T.

Optionally, a surface of the first grating G1 on a side facing the source grating G0 is provided with a metal plating layer, and a material of the metal layer is selected to be a heavy element metal, including: gold, silver, tungsten, lead, or the like. Considering that the large-field grating imaging system is suitable for higher-energy X-rays, it is considered that gold plating is optionally formed as a metal plating layer on the surface of the source grating G0 on the side facing the light source and the surface of the first grating G1 on the side facing the source grating G0, and a part of the X-rays is blocked by the gold plating layer with a certain thickness, thereby reducing the radiation dose of the X-rays. Specifically, as an embodiment of the present invention, the X-ray energy may be selected to be 100kVp, the thickness of the gold-plating layer may be selected to be 150 μm, and the average transmission of the X-ray beam is 1.6%; the average transmission of the X-ray beam was 0.1% at a gold coating thickness of 250 μm. On the other hand, the source grating G0 and the first grating G1 are plated with gold, so that the actual grating is closer to the ideal grating, and the contrast of the imaging system is improved.

As an embodiment of the present invention, the first grating units and the second grating units are respectively stacked in a one-dimensional direction to form a first grating G1 and a second grating G2, and the first grating G1 and the second grating G2 are two-dimensional planar gratings.

Specifically, the first grating unit includes a plurality of stacked grating units stacked one on top of the other. Specifically, the stacking manner may be formed by a plurality of stacked grating units, which may include a double stack, or a stacked combination of three or more stacked grating units. For example, as shown in fig. 4, when the multi-layered grating unit is two stacked grating units (i.e., stacked as a double stack), the first grating unit G is formed by directly combining the first stacked grating unit G 'and the second stacked grating unit G ″ in a stacked manner, or the second grating unit G is formed by directly combining the third stacked grating unit G' and the fourth stacked grating unit G ″ in a stacked manner, and the first grating unit and the second grating unit are two-dimensional planar grating units in a stacked manner. When the first grating units are spliced along a one-dimensional direction, for example, the positive direction of the x-axis, the spliced first grating G1 is a two-dimensional plane grating. When the second grating units are spliced along a one-dimensional direction, such as the positive direction or the negative direction of the x-axis, the spliced second grating G2 is also a two-dimensional plane grating. When the laminate is laminatedIn the case of multi-stack, the corresponding first grating G1 and second grating G2 still satisfy the requirements and characteristics of a two-dimensional planar grating as a whole. The two-dimensional plane grating enables the application range of the system to be wider, and accordingly, the scanning detection mode is more diversified. As a preferred embodiment of the present invention, when the stack is a double stack, the grid shape of the two-dimensional planar first grating G1 is defined by the grating periods p of the first and second stacked grating elements of the first grating element₁₁、p₁₂And its grid direction; and the grid shape of the two-dimensional planar second grating G2 is composed of the grating periods p of the third and fourth stacked grating units of the second grating unit₂₁、p₂₂And its grid direction.

Specifically, for example, since the two-dimensional planar first grating G1/second grating G2 is a stacked combination of stacked grating units of upper and lower layers, accordingly, the direction or shape of the grids of the first grating G1 and the second grating G2 is changed by the grid direction of the stacked grating units, as shown in fig. 4, as an embodiment of the present invention, when the grating grid direction of the first stacked grating unit G' is the horizontal direction and the grating grid direction of the second stacked grating unit G ″ stacked therewith is the vertical direction, the grating grid shape of the first grating unit of the first grating G1 or the second grating unit of the second grating G2 formed by stacking the two is rectangular, that is, when the grating grid directions of the two stacked grating units are perpendicular to each other, the stacked grating grids are rectangular, and when the respective periods of the two stacked grating units are consistent, the rectangular is square. Similarly, as another embodiment of the present invention, when the grating grid directions of the two stacked grating units are at a non-right angle, the stacked grating grid shapes are parallelograms, and when the respective periods are the same, the parallelograms are rhombuses. By laminating the one-dimensional gratings, two-dimensional gratings of various grid shapes can be obtained.

Another aspect of the present invention provides an imaging scanning method applied to the above-mentioned grating imaging system, as shown in fig. 5, the method includes:

s510, the control system moves along the vertical direction to scan the imaging irradiation position between the first grating G1 and the second grating G2;

s520, exposing the imaging irradiation position at a specific scanning height;

and S530, extracting the exposed data information to acquire imaging.

The grating imaging system comprises: the source grating G0 is used for converting incoherent light emitted by the light source into coherent light, and the first grating G1 formed by splicing a plurality of first grating units is used for acquiring a first image after the coherent light passes through the first grating G1; the second grating G2 is formed by splicing a plurality of second grating units and is used for operating the first imaging to obtain a second imaging; an imaging irradiation position is arranged between the first grating G1 and the second grating G2, and the source grating G0, the first grating G1 and the second grating G2 form a light path to form a system. Therefore, the invention can realize that the imaging irradiation position is kept still, and the scanning imaging of the object to be detected on the imaging irradiation position is realized by moving the source grating G0\ G1\ G2 of the grating imaging system. In other words, compared with the traditional mode that the position of the object to be detected moves and the grating is kept still, the method has stronger applicability, for example, the traditional grating imaging mode can only be a lying shooting mode, and various forms such as the lying shooting mode or the standing shooting mode can be realized through the invention.

In addition, as a preferable mode of the present invention, the present invention adopts a trigger type exposure-collection mode, the exposure of the X-ray source is started only when an external trigger signal is received, and the integral collection is stopped by simultaneously triggering the detector after the exposure is finished. Therefore, all X-rays are fully utilized, and the detector only generates the X-rays during integral acquisition; in addition, the tube current of the X-ray machine is selectively improved, so that the single exposure time can be set to be very short (dozens of milliseconds), the scanning process is more compact, and the scanning efficiency is higher. Accordingly, the present invention may also be used in a non-triggered exposure-capture mode, such as a continuous exposure mode.

Finally, the scanning method of the present invention needs the system to be completed based on certain physical devices, as shown in fig. 6A and 6B, the X-ray source, the grating group (source grating G0/first grating G1/second grating G2) and the detector are all fixed on a mechanical arm, and the moving directions of the mechanical arms can be different, for example, the mechanical arm fixing the grating group can move up and down along the mechanical arm in the z-axis direction, the mechanical arm fixing the source grating G0 and the first grating G1 can move closer or farther in the X-axis direction relative to the second grating G2, and the mechanical arm (i.e., the nano-moving stage) of the second grating G2 can move in the y-axis direction relative to the source grating G0 or G1, and all the mechanical arms can be controlled by a servo motor, so as to realize the movement in the vertical direction of the system to realize the scanning.

As an embodiment of the present invention, exposing an imaging exposure site at a specific scan height includes: when the system reaches a certain scan height, the second grating G2 is controlled to perform a phase step scan in the horizontal direction to reach a certain scan step length, the imaging exposure position is exposed.

Specifically, as shown in fig. 6A and 6B, when the system scans the imaging irradiation position from bottom to top, the servo motor drives the system to move in the z-axis direction so that the optical axis (the connection line formed by the center of the source grating G0, the center of the first grating G1, and the center of the second grating G2) reaches the first scanning height, the servo motor stops, the nano moving stage drives the second grating G2 to perform phase stepping scanning in the y-axis direction, the servo motor continues to operate after the stepping scanning is finished, the system is driven to move to the second scanning height, and the above operations are repeated, and when the imaging irradiation position is not reached to the first scanning height, the imaging irradiation position is exposed to obtain a single image. The effective imaging of at least two scans are superposed to obtain the scanning imaging result required by the invention, namely discontinuous phase stepping scanning.

As an embodiment of the present invention, exposing an imaging exposure site at a specific scan height includes: before the system reaches a specific scanning height, the second grating G2 is controlled to perform phase stepping scanning in the horizontal direction to reach a specific scanning step; and exposing the imaging exposure site after the system reaches a particular scan height.

Specifically, as shown in fig. 6A and 6B, the second grating G2 is moved by the nano moving stage one step in the y-axis direction (optionally, the total length of one phase step is set as one period of G2, and then if this period is divided equally, the minimum step (phase step, i.e., step) may be 3.), the servo motor drives the system grating group to move stably at a constant speed from bottom to top (or from top to bottom) in the z-axis direction, each time the system scanning height increases by a fixed distance to reach a specific height, the X-ray machine exposes once, the detector collects once, and when the system scanning height reaches the maximum (or minimum), the step of the second grating G2 is moved once again, and the above operations are repeated in reverse direction. The effective imaging of at least two scans are superposed to obtain the scanning imaging result required by the invention, namely continuous phase stepping scanning. Compared with discontinuous phase stepping scanning, the time consumed by continuous scanning is shorter, and the total scanning speed is greatly improved. It should be noted that in this case, both scanning modes are applicable regardless of whether the raster grid direction is horizontal or vertical.

The large-area grating imaging system can adopt the discontinuous phase step scanning mode and can also reduce the whole scanning time through continuous phase step scanning. In view of the limitation of the scanning efficiency improved by the above scanning method, the present invention provides a fast scanning method as another embodiment of the present invention.

As an embodiment of the present invention, exposing an imaging exposure site at a specific scan height includes: in the first specificationCompleting the first exposure at the scanning height, and completing the second exposure at a second specific scanning height; wherein, the height difference h between the nth and the (n + 1) th first grating units of the first grating G1_n,n+1Satisfies the following formula (7):

h_n,n+1＝m·Δh

wherein m is a positive integer, Δ h is a third distance between the first specific scanning height and the second specific scanning height; height difference h between nth and n +1 th second grating units of second grating G2_n,n+1Satisfies the following formula (8):

where m is a positive integer, l is the first pitch between the source grating G0 and the first grating G1, p2 is the period of the second grating G2, and N is the number of phase steps of the second grating G2.

In order to realize fast scanning, as an embodiment of the present invention, n first grating units with the same properties, such as the grid direction, the period, and the like, may be sequentially arranged in the vertical direction (Z-axis direction) to form a first grating G1, wherein the first grating units may be arranged separately so that a certain gap is maintained between adjacent grating units, or may be directly spliced into a complete grating. Specifically, the process of the split arrangement requires a certain distance to be spatially maintained at the time of mechanical installation. The height difference between the adjacent first grating units of the first grating G1 is h_1,2,、h_2,3、……h_n,n+1. When n is 3, three independent first grating units with consistent period and horizontal grid direction form a first grating G1, and the system is exposed and collected once every deltah distance when moving in the z-axis direction, wherein m and l are positive integers, and p is shown in FIG. 7₂The period of the second grating G2, N is the number of phase steps. Each first grating unit respectively realizes the scanning of the object to be measured of the imaging irradiation position, and the height difference between the first grating units just accords with the phase stepping. For the same height area of the object, when each first grating unit scans to the height, the grating grids of the first grating units are just shifted by one step of phase stepping, so that the method indirectly realizes the purpose of scanning the objectA phase stepping process at this scan height is achieved. At the moment, the system only needs to scan once in the vertical direction, a plurality of grating units are distributed and scanned at each scanning height, and the collected imaging results can form the same displacement curve, so that information is extracted to obtain a final imaging image.

Example 2:

another aspect of the present invention provides a grating imaging system, the system comprising a source grating G0, a first grating G1, and a second grating G2 arranged in sequence along an optical path, wherein: at least one of the source grating G0, the first grating G1, and the second grating G2 is a curved grating, and an imaging illumination position is provided between the first grating G1 and the second grating G2.

As an embodiment of the present invention, as shown in fig. 8, the system includes a source grating G0, a first grating G1, and a second grating G2, which are sequentially arranged along the optical path, to form a grating group of the system, where: the source grating G0 is used for converting incoherent light emitted by the light source into coherent light; a first grating G1 for obtaining a first image after the coherent light passes through the first grating G1; and a second grating G2 for operating on the first image to acquire a second image.

Specifically, as shown in fig. 8, as an embodiment of the present invention, the light source is an X-ray light source, the X-ray beam emitted by the light source generates a series of partially coherent linear light sources through a source grating G0, the source grating G0 makes the system applicable to coherent light sources or incoherent light sources, and in this case, the source grating G0 may be a plane grating; the first grating G1 is a phase grating or an absorption grating, the second grating G2 is an analyzer grating, and at this time, the first grating G1 and the second grating G2 are curved gratings. The X-ray passes through the first grating G1 to generate a self-imaging, namely a first imaging, of the first grating G1 at a certain distance; when an object to be irradiated is arranged on an imaging irradiation position arranged between the first grating G1 and the second grating G2, the second imaging is the imaging of the X-ray camera irradiated on the object through the first grating G1 and then through the second grating G2, and the imaging is observed on a detector.

As another embodiment of the present invention, at least one of the source grating G0, the first grating G1, and the second grating G2 is a curved grating. Since the light emitted from the light source can be understood as a cone beam in the system, when the cone beam passes through the source grating G0 and the first grating G1 and is further irradiated to the imaging irradiation site, light loss occurs, for example, reflection, absorption, diffraction, and the like on the source grating G0 and the first grating G1 all affect the beam, and if a large dose of X-rays is used for irradiation, an excessive wind direction is likely to occur. On the other hand, the light beam direction of the plane grating to the cone-shaped light beam cannot be perpendicular to the grating direction of the grating, so that the loss of a small-dose X-ray beam is too large when the small-dose X-ray beam passes through the plane grating, the dose is easy to be too small, and the imaging effect is poor. The curved grating can fully realize the utilization of the cone beam, can accurately control the dosage of the light beam, and reduces the loss caused when the light beam passes through the source grating G0 and the first grating G1. Finally, in the case of using the curved grating, the light loss caused by the source grating G0 and the first grating G1 is small, so that the influence thereof can be ignored when controlling the radiation dose, and the radiation dose can be controlled more easily by focusing only on the dose of the X-ray source. Therefore, the design of the curved grating enables the X-ray to be more fully utilized, the loss of the X-ray in a light path is reduced, the application of the small-dose X-ray is realized, the radiation dose is further reduced, and the radiation dose is easier to control. And finally, the curved surface grating is beneficial to the clearer second imaging data received by the detector, so that the imaging effect is better. Accordingly, at least one of the source grating G0, the first grating G1, and the second grating G2 may be selected to be a curved grating. The distance between the source grating G0 and the light source may be only a few centimeters at most due to the close design of the light source, and on the other hand, the size of the source grating G0 is small, so the source grating G0 may be a planar grating.

In an embodiment of the invention, the first grating G1 is formed by splicing a plurality of first grating G1 units along a certain curve direction, the first radian of the first grating G1 is α, the second grating G2 is formed by splicing a plurality of second grating G2 units along the curve direction, and the second radian of the second grating G2 is β.

In the grating manufacturing process, the first grating G1 and the second grating G2 cannot be directly manufactured at one time, and grating sub-blocks, that is, grating units, need to be manufactured first. The source grating G0 is very close to the X-ray source, so the size requirement is low, and the processing can be finished at one time; the size of the first grating G1 and the second grating G2 is large, and the first grating G1 formed by splicing a plurality of first grating G1 units and the second grating G2 formed by splicing a plurality of second grating G2 units need to be spliced by 2 or more grating sub-blocks, and a large-area grating meeting requirements is obtained in a splicing mode, wherein the size, the grating period, the grating direction and the like of the first grating G1 unit and the second grating G2 unit can be respectively inconsistent. In addition, regarding the splicing mode, a certain gap can be formed between the adjacent grating units so as to meet various imaging requirements. In addition, since the first grating G1 or the second grating G2 is a curved grating, the splicing direction of the first grating G1 unit or the second grating G2 unit is a curved direction, and the straight splicing manner is not limited in the case of ensuring that the first grating G1 or the second grating G2 is a curved grating.

As an embodiment of the present invention, the first grating G1 unit or the second grating G2 unit is a first planar grating unit or a second planar grating unit, and the first planar grating unit or the second planar grating unit is spliced along a specific curve direction to form a first grating G1 or a second grating G2; or the first grating G1 unit or the second grating G2 unit is a first curved grating unit or a second curved grating unit, and the first curved grating unit or the second curved grating unit is spliced along a specific curve direction to form a first grating G1 or a second grating G2.

Specifically, as shown in fig. 9, the first grating G1 is formed by splicing a plurality of first grating G1 units G10 along the direction of the curve S1, and the arc length of the first grating G1 unit G10 corresponds to S1₀When the n first grating G1 units G10 are spliced along the direction of the curve S1, the arc length S1 is n × S₀In the curve splicing mode, the value of the corresponding first radian is related to the corresponding center O, the value of the first radian is a mathematical radian value which can be α, and when r is equal to r, r is equal to r₁When the first grating G1 has an arc length of S₁＝r₁X α. accordingly, the second radian of the second grating G2 can be β when r is equal to r₂Then, the arc length of the second grating G2 may be S₂＝r₂×β。

Specifically, each grating unit is spliced along a curve direction and includes two combination forms of a planar grating unit and a curved grating unit, the first grating G1 unit or the second grating G2 unit is a first planar grating unit or a second planar grating unit, the first planar grating unit or the second planar grating unit is spliced along a specific curve direction to form a first grating G1 or a second grating G2, at this time, the first grating G1 or the second grating G2 is a curved grating, as shown in fig. 9, the first grating G1 unit G10 of the first grating G1 is a planar grating, the plurality of first grating G1 units G10 are spliced along a direction of a curve S1 to form a first grating G1, and the first grating G1 is a curved grating. Correspondingly, the first grating G1 unit or the second grating G2 unit is a first curved grating unit or a second curved grating unit, and the first curved grating unit or the second curved grating unit is spliced along a specific curve direction to form a first grating G1 or a second grating G2, and at this time, the first grating G1 or the second grating G2 is also a curved grating.

The grating units are spliced along the linear direction and comprise two combination forms of a plane grating unit and a curved surface grating unit, and when the plane grating units are spliced along the linear direction, the obtained combined grating is a plane grating; after the curved surface grating units are spliced along the straight line direction, the obtained combined grating is a combined grating with a plurality of curved surface gratings distributed along the straight line, and the projection of the combined grating on the plane vertical to the straight line direction is a plane grating. In addition, the plurality of first planar grating units or second planar grating units are spliced in the linear direction to form the first grating G1 or the second grating G2, and the first grating G1 and the second grating G2 are directly mechanically bent, so that the first grating G1 or the second grating G2 with a curved surface can also be obtained.

As an embodiment of the present invention, a plurality of first planar grating units or a plurality of second planar grating units are respectively spliced in a two-layer manner along a specific curve direction to form a first grating G1 or a second grating G2; or a plurality of first curved surface grating units or a plurality of second curved surface grating units are spliced in a double-layer mode along a specific curve direction to form a first grating G1 or a second grating G2; the first grating G1 or the second grating G2 is a two-dimensional curved grating.

Specifically, the "double-layer mode" may be that the first planar grating unit or the second planar grating unit includes an upper planar grating unit and a lower planar grating unit which are stacked and combined. At this time, the first planar grating unit or the second planar grating unit is a two-dimensional planar grating unit. When the first planar grating unit or the second planar grating unit is spliced along a specific curve direction, the spliced first grating G1 or second grating G2 is a two-dimensional curved grating. Correspondingly, the "double-layer mode" may also be that the first curved surface grating unit or the second curved surface grating unit includes an upper curved surface grating unit and a lower curved surface grating unit which are superposed and combined. At this time, the first curved surface grating unit or the second curved surface grating unit is the two-dimensional curved surface grating unit. When the first curved surface grating unit or the second curved surface grating unit is spliced along the specific curve direction, the spliced first grating G1 or second grating G2 is a two-dimensional curved surface grating. The two-dimensional plane grating enables the application range of the system to be wider, and accordingly, the scanning detection mode is more diversified.

Specifically, the "curve direction" may be a curve extending direction in any one radian, and the extending direction may be changed, that is, the curve thereof is not limited to a curve of a single radian, and may be a curve including a plurality of radians. Therefore, the curved surface grating can be spliced at any angle according to the requirement.

As an embodiment of the present invention, the grid shape of the first grating G1 is formed by the grating periods p of the first and second stacked grating units of the first grating G1 unit₁₁、p₁₂And its grid direction; and the grid shape of the second grating G2 is composed of the grating periods p of the third and fourth stacked grating units of the second grating G2 unit₂₁、p₂₂And its grid direction.

Specifically, for example, the two-dimensional curved surface first grating G1/second grating G2 is a laminated combination of upper and lower laminated grating units, and accordingly, the direction or shape of the grids of the first grating G1 and the second grating G2 are changed by the grid direction of the stacked grating units, and as an embodiment of the present invention, when the grating grid direction of the first curved laminated grating unit is a horizontal direction and the grating grid direction of the second curved laminated grating unit laminated with the first curved laminated grating unit is a vertical direction, the grating grid shape of the first grating G1 unit of the first grating G1 or the second grating G2 unit of the second grating G2 formed by laminating the first curved laminated grating unit and the second curved laminated grating unit is a rectangle, that is, when the grating grid directions of the two curved-surface laminated grating units are perpendicular to each other, the laminated curved-surface grating grid shape is a rectangle, and when the respective periods are consistent, the rectangle is a square. Similarly, as another embodiment of the present invention, when the grating grid directions of the two curved-surface stacked grating units form a non-right angle with each other, the stacked curved-surface grating grid shape is a parallelogram, and when the respective periods are consistent, the parallelogram is a rhombus. By laminating the one-dimensional curved surface grating in a specific curve direction, two-dimensional curved surface gratings in various grid shapes can be obtained. Accordingly, when the one-dimensional plane grating is laminated in a specific curve direction, two-dimensional curved surface gratings in various grid shapes can be obtained.

As an embodiment of the present invention, the first grating G1 and the second grating G2 are both curved surface gratings, and satisfy the following formula:

wherein s is₁Is the arc length, h, of the first grating G1₁Is the height of the first grating G1; s₂Is the arc length, h, of the second grating G2₂Is the height of the second grating G2; r is₁Is a first separation, r, between the source grating G0 and the first grating G1₂A second pitch between the first grating G1 and the second grating G2.

Specifically, as shown in fig. 8, in consideration of the fact that the difficulty of grating splicing is high in practice, it may be considered that the grating is spliced along a specific curve direction at present, that is, under the condition that the second grating G2 can effectively obtain the image of the first grating G1, the splicing directions of the plurality of first planar grating units or the splicing directions of the plurality of second planar grating units are consistent, and it is sufficient to ensure that the grating groups are distributed along a reference optical path (i.e., an optical path center line) formed by the center G01 of the source grating G0, the center G11 of the first grating G1, and the center G21 of the second grating G2. As shown in fig. 8, the first grating G1 and the second grating G2 are both curved gratings. Wherein s is₁Is the arc length, h, of the first grating G1₁Is the height of the first grating G1; s₂Is the arc length, h, of the second grating G2₂Is the height of the second grating G2; the arc length of the grating can be understood as, for example, when an orthographic projection of a grating on a plane is a rectangular grating shadow, the length of the edge of the grating corresponding to the corresponding width is the arc length of the grating, and the length of the edge of the grating corresponding to the corresponding height is the height of the grating. As an embodiment of the present invention, when the third distance between the source grating G0 and the second grating G2 is L, a certain arc-shaped side r₁＝L－r₂Or r is₂＝L－r₁In the embodiment of the present invention, r₁Is a first separation distance, r, between the source grating G0 and the first grating G1₂A second pitch between the first grating G1 and the second grating G2. At this time, an included angle formed by the first grating G1 or the second grating G2 with respect to the light source (which can be regarded as a particle) may be inconsistent with an included angle corresponding to an arc obtained by a mathematical calculation formula of an arc length corresponding to the first grating G1 or the second grating G2.

As an embodiment of the invention, the second distance r between the first grating G1 and the second grating G2₂The following formula is satisfied:

wherein r is₁A first separation between the source grating G0 and the first grating G1; p is a radical of₀、p₁、p₂The periods of the source grating G0, the first grating G1 and the second grating G2 are respectively, lambda is the X-ray wavelength, n is a constant, n is an odd number when the first grating G1 is a phase grating, n is an even number when the first grating G1 is an absorption grating, η is another constant related to the grating type, η is 1 when the first grating G1 is a pi/2 phase grating or an absorption grating, and the first grating G1 is 2 when the first grating G1 is a pi phase grating.

In addition, the first grating G1 can be selected as a curved phase grating or a curved absorption grating, the second grating G2 can be selected as a curved analysis grating, and the second grating G2 is placed at a specific distance behind the first grating G1, wherein the specific distance satisfies the relationship among the period of each component grating, the wavelength of incident X-rays and the characteristic of the grating, such as the relationship among the value of n or η and the type of the grating.

In order to make the grating imaging technique more suitable for the incoherent X-ray source, the moire fringe generated by the projection of the first grating G1 and the second grating G2 can be selected to realize the imaging,such a system is called a "geometric projection system" in which the first grating G1, when chosen as an absorption grating, i.e. n is an even number and η is 1, the above formula can be transformed accordingly, i.e. with its system parameters, i.e. the second separation r between the first grating (G1) and the second grating (G2)₂The formula needs to be satisfied:

wherein r is₁A first pitch between the source grating (G0) and the first grating (G1); p is a radical of₀、p₁、p₂The periods of the source grating (G0), the first grating (G1) and the second grating (G2), respectively.

Comparing the above formula system with the geometric projection system, it can be known that the first curved grating G1 usually employs a phase grating, and a specific system X-ray energy needs to be designed to correspond to the phase grating to realize modulation, and the second grating G2 must be placed at a specific distance behind the first grating G1; the latter relaxes the requirements of system parameters, and the system X-ray energy and the position of the second grating G2 are not limited, i.e. the distance between the first grating G1 and the second grating G2 does not need to be fixed, which is more suitable for practical applications, for example, a larger object to be detected is arranged at the imaging irradiation position between the first grating G1 and the second grating G2, in the embodiment of the present invention, the first grating G1 and the second grating G2 are curved gratings. As an embodiment of the present invention, the large-field grating imaging system preferably adopts the design of the above-mentioned geometric projection system.

As an embodiment of the invention, the system further comprises a detector, the size of the pixel of the detector is larger than the period of the first grating G1, and the shape of the detector is curved. Specifically, as shown in fig. 8, the X-ray passing through the first grating G1 produces a self-image of the grating over a distance, i.e., a first image; at the detector T the pixel size is much larger than the period P of the first grating G1₁When the second grating G2 is adopted, the first grating G can be realized1 to obtain a second image, which is observed by a detector T. In the embodiment of the present invention, the first grating G1 or the second grating G2 may be a curved grating, wherein at least the detector disposed opposite to the second grating G2 is designed to have a corresponding curved shape structure.

As an embodiment of the present invention, the curved surface grating is an S-shaped curved surface. As an embodiment of the present invention, when the first gratings G1 or the second gratings G2 are spliced along the S-shaped curved line direction, the first gratings G1 or the second gratings G2 are curved gratings, and the curved surface is S-shaped. At least 2 irradiation imaging positions can be formed for the first grating G1 or the second grating G2 with the S-shaped curved surface, and more imaging irradiation positions can be obtained in a limited space, so that a plurality of imaging irradiation positions can be scanned at the same time, and the scanning efficiency is further improved.

As an embodiment of the present invention, the grid orientation of the curved surface grating is consistent with the optical path direction. As an embodiment of the invention, the grid orientation of the curved surface grating can be consistent with the extending direction of the light path, so that the small-dose X-ray beam can directly pass through the grating grid along the light path without being reflected by the inner wall of the grid when entering the grid. At this time, the X-ray beam blocked by other positions of the grid is not easy to enter the grid, and can be directly reflected or absorbed. Therefore, the mode has small loss, and when the light source emits small dose of X rays, the dose is not easy to be too small, so that the imaging effect is poor, and the problem of large-angle incidence is avoided. The curved grating can fully realize the utilization of the cone beam, can accurately control the dosage of the light beam, and reduces the loss caused when the light beam passes through the source grating G0 and the first grating G1.

Another aspect of the invention provides a novel large field of view grating imaging system. The system manufactures the large-area curved surface grating meeting the requirements of large-field imaging and the like in a splicing mode, can realize the large-area imaging field matched with clinical medicine, and realizes scanning imaging of a large-size sample and even a human body; in addition, the depth-to-width ratio of the grating is improved to be suitable for the X-ray with higher energy, and the imaging irradiation position is arranged between the first grating G1 and the second grating G2 to reduce the radiation dose of the object and reduce the generation of ineffective X-ray; and the design of the curved surface grating enables the X-ray to be more fully utilized, reduces the loss of the X-ray in a light path, realizes the application of the small-dose X-ray, further reduces the radiation dose, and is easier to realize the controllability of the radiation dose. Practical experimental data show that the system maintains good image quality, the whole scanning time is reduced to a level close to that of a clinical X-ray chest film, and meanwhile, the radiation dose is well controlled; in summary, the large-field grating imaging system has the advantages and characteristics of large imaging field of view, high scanning speed, low radiation dose and the like. Another aspect of the present invention provides a raster imaging scanning method applied to the raster imaging system.

The invention can realize that the imaging irradiation position is positioned between the first grating G1 and the second grating G2 and is kept still, and the scanning imaging of the object to be detected on the imaging irradiation position is realized by moving the source grating G0\ the first grating G1\ the second grating G2 of the grating imaging system. In other words, compared with the traditional mode that the position of the object to be detected moves and the grating is kept still, the method has stronger applicability, for example, the traditional grating imaging mode can only be a lying shooting mode, and various forms such as the lying shooting mode or the standing shooting mode can be realized through the invention. The scanning speed is faster, and the scanning efficiency is higher.

In addition, the invention adopts a trigger type exposure-acquisition mode, the X-ray source can start exposure only when receiving an external trigger signal, and the detector is triggered to stop integral acquisition at the same time after the exposure is finished. Therefore, all X-rays are fully utilized, and the detector only generates the X-rays during integral acquisition; in addition, the tube current of the X-ray machine is selectively improved, so that the single exposure time can be set to be very short (dozens of milliseconds), the scanning process is more compact, and the scanning efficiency is higher.

Finally, the scanning method of the present invention needs to be completed by the system based on certain physical devices, as shown in fig. 6A and 6B, the X-ray source, the grating group (source grating G0/first grating G1/second grating G2) and the detector are all fixed on the mechanical arm, and the moving directions of the mechanical arm may be different, for example, the mechanical arm fixing the grating group may move up and down along the mechanical arm in the z-axis direction, the mechanical arm fixing the source grating G0 and the first grating G1 may move closer or farther in the X-axis direction relative to the second grating G2, and the mechanical arm (i.e., the nano-moving stage) of the second grating G2 may move in steps in the y-axis direction relative to the source grating G0 or the first grating G1, and all the mechanical arms may be controlled by the servo motor, so as to realize the movement in the vertical direction of the system to.

As an embodiment of the present invention, based on the above-mentioned raster imaging system, a raster imaging scanning method may be correspondingly designed, and the scanning method may implement fast scanning, and the scanning method may include:

the control system moves along the vertical direction to scan the imaging irradiation position between the first grating G1 and the second grating G2; exposing the imaging irradiation position at a specific scanning height; extracting the exposed data information to obtain imaging; wherein, the exposure is a trigger type exposure.

Specifically, as shown in fig. 9, in an embodiment of the present invention, when the grid direction of the first grating G1 is along the vertical direction, in order to reduce the influence of the large-angle incidence of the X-rays in the horizontal direction, the first grating G1 is designed to be bent along the horizontal direction, i.e., to be spliced along a certain curve direction. A curved surface grating first grating G1 of a concentric circle with the X-ray source as the origin point O can be obtained.

And performing fast scanning, and optionally performing down-sampling on scanning results of adjacent scanning heights to obtain an equivalent approximate phase stepping displacement curve, wherein at the moment, two scanning modes of unidirectional and bidirectional phase stepping can be adopted, and the method specifically comprises the following steps:

1) unidirectional phase stepping fast scan: taking the scanning of the system from bottom to top as an example, the servo motor drives the source grating G0 and the first grating G1 of the grating group to move up and down stably at a constant speed along the vertical direction, the nano mobile platform drives the second grating G2 and the detector of the grating group to move simultaneously, and it can be set that when the servo motor moves a fixed distance to reach a specific height, the nano mobile platform just moves by one step length, and at the moment, the imaging irradiation position is directly exposed. And finally, when the nano mobile station moves for a complete period, returning to the original point to repeatedly move and expose, and then completing the scanning process of the unidirectional phase stepping fast scanning.

2) Bidirectional phase step fast scan. Taking the scanning of the system from bottom to top as an example, the servo motor drives the source grating G0 and the first grating G1 of the grating group to move up and down stably at a constant speed along the vertical direction, the nano mobile platform drives the second grating G2 and the detector of the grating group to move simultaneously, and it can be set that when the servo motor moves a fixed distance to reach a specific height, the nano mobile platform just moves by one step length, and at the moment, the imaging irradiation position is directly exposed. And finally, when the nano moving table moves for a complete period, the nano moving table starts to move reversely and expose, and the scanning process of bidirectional phase stepping fast scanning is completed.

A fast scan is performed and optionally the scan results in the horizontal direction are down-sampled to obtain an equivalent approximated displacement curve. For example, a plurality of grating sub-blocks can be arranged in the vertical direction, can be arranged separately, and can also be spliced into a complete grating. Wherein, the source grating G0 and the first grating G1 in the first grating G1 can be completely parallel in the vertical direction, and the grids are aligned with each other, and if the height difference between them is h, the following formula is satisfied:

h＝m·Δh

where m is a positive integer and Δ h is the scan height interval in the vertical direction. Accordingly, the height difference between the second grating G2 units of the second grating G2 is also h.

Example 3:

yet another aspect of the present invention provides a grating imaging system, comprising a source grating G0, a first grating G1, and a second grating G2 arranged in that order along an optical path, wherein:

the first grating G1 comprises a plurality of first grating units which are spliced in a staggered mode; and/or the second grating G2 comprises a plurality of second grating units spliced with each other in a staggered way,

and the first grating units or the second grating units are staggered along the grid direction of the first grating units or the second grating units correspondingly.

Specifically, as shown in fig. 10, the light source is an X-ray light source, and the X-ray beam emitted from the light source generates a series of partially coherent linear lights through the source grating G0. In addition, the X-ray source of the present invention can be selected from incoherent conventional X-ray sources, such as general X-ray machines and medical X-ray tubes, so as to be better suitable for practical use, because such X-ray sources are generally the worst performance. Of course, other light sources with better coherence and monochromaticity, such as synchrotron radiation or microfocus light sources, may be selected, and the source grating G0 may not be used.

In order to achieve a fast scan, the scan time is shortened, which also reduces the dose. The source grating G0 allows the system to be used with either coherent or incoherent light sources; the position of the source grating G0 needs to be as close as possible to the light source. The period of the source grating G0 is similar or similar to that of the first grating G1 or the second grating G2, the grating area needs to cover the light source, and the thickness of the source grating G0 is similar to that of the first grating G1.

As an embodiment of the present invention, the first grating G1 is a phase grating or an absorption grating, the second grating G2 is an analyzer grating, and the X-ray passing through the first grating G1 generates a self-imaging, i.e., a first imaging, of the first grating G1 at a certain distance; when an object to be irradiated is arranged on an imaging irradiation position arranged between the first grating G1 and the second grating G2, the second imaging is the imaging of the X-ray camera irradiated on the object through the first grating G1 and then through the second grating G2, and the imaging is observed on a detector.

In the grating manufacturing process, the first grating G1 and the second grating G2 cannot be directly manufactured at one time, and grating sub-blocks, that is, grating units, need to be manufactured first. The source grating G0 is very close to the X-ray source, so the size requirement is low, and the processing can be finished at one time; the first grating G1 and the second grating G2 are large in size and need to be tiled by 2 or more blocks of grating sub-blocks. In the embodiment of the present invention, as shown in fig. 10, that is, the first grating G1 formed by splicing a plurality of first grating units along the vertical direction and the second grating G2 formed by splicing a plurality of second grating units in a staggered manner in the vertical direction obtain a large-area grating meeting the requirement by splicing, where the size, grating period, grating direction, etc. of the first grating unit and the second grating unit may not be the same. As shown in fig. 10, 4 first grating units G11, G12, G13, and G14 are spliced in the vertical direction to form a first grating G1, 7 second grating units G21, G22, G23, G24, G25, G26, and G27 are spliced in a staggered manner in the vertical direction to form a second grating G2, and form a grating group with the source grating G0, and the grating group forms an imaging optical path with the light source, the imaging irradiation position, and the detector. The mutual offset splicing may be mutual offset splicing of two mutually adjacent grating units of the first grating G1 or the second grating G2, or mutual offset splicing of two or more mutually non-adjacent grating units. The dislocation can be gradual dislocation or staggered dislocation. As shown in fig. 10, the second grating G2 may be formed by splicing a plurality of second grating units from top to bottom in a gradually staggered manner, and the grid direction of the first grating unit or the second grating unit may be the horizontal direction. Correspondingly, the first grating G1 and the second grating G2 may also be formed by splicing a plurality of first grating units or second grating units one by one from top to bottom in a staggered manner in the vertical direction (Z axis), that is, the first grating G1 and the second grating G2 may be spliced according to the scanning requirements of the first grating units and the second grating units. It should be understood by those skilled in the art that the splicing manner shown in fig. 10 is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Regarding the splicing manner, the grating units adjacent to each other may have a certain gap therebetween (which is equivalent to separate arrangement on a grating background, and the grating background may be a portion for fixed splicing of the grating units, and may be a portion of a large-area grating in the system), so as to meet various imaging requirements.

And the first grating units or the second grating units are staggered along the grid direction of the first grating units or the second grating units correspondingly. As shown in fig. 10, 7 second grating units G21, G22, G23, G24, G25, G26, and G27 are spliced in a staggered manner in the vertical direction to form a second grating G2, and then the grating grid directions of the 7 second grating units may be horizontal directions, which correspond to the horizontal directions in fig. 10 where the plane of the second grating background is perpendicular to the Z axis (longitudinal direction), that is, the 7 second grating units are all staggered from each other in the horizontal directions.

Through the design of dislocation concatenation, can realize when carrying out a scan to large area grating on the whole, can be equivalent to wherein each grating unit respectively realizes the scanning separately, the dislocation difference of each adjacent grating unit can keep certain relation with the scanning phase step number N of large area grating, for example the dislocation difference is nN, N is the positive integer. For the same height area of the object to be detected, when each grating unit reaches the scanning height in the imaging scanning process, the grating grids of the grating units are just dislocated by one or more step lengths of the phase stepping number, and the phase stepping process on the scanning height is indirectly realized. Namely, the scanning imaging process of the whole large-area grating is completed.

As an embodiment of the present invention, when the first grating units and the second grating units are respectively spliced in a staggered manner along a one-dimensional direction, the first grating G1 and the second grating G2 satisfy the following formula:

wherein x is₁Is the width, h, of the first grating G1₁Is the height of the first grating G1; x is the number of₂Is the width, h, of the second grating G2₂Is the height of the second grating G2; l is a first pitch between the source grating G0 and the first grating G1, and d is a second pitch between the first grating G1 and the second grating G2, as shown in fig. 10. Specifically, the width or height of the first grating G1 or the second grating G2 can be interchanged in different arrangements of grating units, such as in a horizontal plane, the first arrangement, x₁Is the width, h, of the first grating G1₁Is the height of the first grating G1, and is rotated by 90 degrees to form a second arrangement mode, x₁Is the height, h, of the first grating G1₁The width of the first grating G1. In addition, the difference in the positions of the grating units spliced with each other with a shift is very small, and is generally related to the number of phase steps (the difference in the positions of n). As shown in fig. 10, the second grating G2 is formed by 7 second grating units G21, G22, G23, G24, G25, G26, and G27 by staggered splicing, where a misalignment difference Δ x between the second grating unit G21 and the second grating unit G27 is nN, N is a positive integer, N is a phase step number of the second optical dispersion, and N is generally in the micrometer scale, that is, the misalignment difference Δ x is generally in the micrometer scale, and is equal to the first pitch l and the second pitch d in the centimeter scale, and the width x of the second grating G2 in the centimeter scale₂Height h of the second grating G2₂In contrast, it is almost negligible. Therefore, it still satisfies the above formula. In addition, based on the above formula, the first grating G1 and the second grating G2 have an area proportional relationship, and the first grating G1 has an area S₁And the second grating G2 area S₂The following formula is satisfied:

it should be noted that, when the first grating G1 and the second grating G2 are the first grating unit and the second grating unit, respectively, they are ordinary grating imaging systems, but their relationship with each other still satisfies the above formula.

As an embodiment of the present invention, the second pitch d between the first grating G1 and the second grating G2 satisfies the following formula:

In addition, the grating G1 can be selected as a phase grating or an absorption grating, the second grating G2 can be selected as an analysis grating, and the second grating G2 is placed at a specific distance behind the first grating G1, wherein the specific distance satisfies the above formula and is related to the period of each component grating, the wavelength of incident X-rays and the characteristics of the grating, such as the value of n or η, and the type of the grating.

As an embodiment of the present invention, in order to make the grating imaging technology more suitable for the incoherent X-ray source, the moire fringes generated by the superposition of the projection of the first grating G1 and the second grating G2 may be selected to realize the imaging, and such a system is called a "geometric projection system", in this system, when the first grating G1 is selected as the absorption grating, i.e. n is an even number, η is 1, therefore, the above formula may be transformed accordingly, i.e. its system parameters, and the second distance d between the first grating G1 and the second grating G2, satisfy the following formula:

Comparing the system of the above formula with the geometric projection system, it can be seen that the first grating G1 usually employs a phase grating, a specific system X-ray energy is required to be designed to correspond to the phase grating to realize modulation, and the second grating G2 must be placed at a specific distance behind the first grating G1; the latter relaxes the system parameter requirements, the system X-ray energy and the position of the second grating G2 are not limited, i.e. the distance between the first grating G1 and the second grating G2 does not need to be fixed, which is more suitable for practical applications, for example, a larger object to be detected is arranged at the imaging irradiation position between the first grating G1 and the second grating G2. The large field-of-view grating imaging system preferably employs the design of the geometric projection system as an embodiment of the present invention.

In addition, as a preferable aspect of the present invention, the period of the second grating G2 cannot be too large to prevent the resolution from being lowered and the problem of poor image definition being caused. Meanwhile, the second distance d cannot be too small to realize the detection of the large-volume object, and should be close to the first distance l. Therefore, as a preferable design of the embodiment of the present invention, l/d can be designed to be 5: 4. And 1:1 is preferable when l/d is used. l: d, determining the grating period according to the formula. Wherein the projection (or self-imaging) period of the first grating G1 is smaller than the detector period, and the imaging is almost invisible; when a second grating G2 is added between the first grating G1 and the detector, moire fringes are formed, the period of the projection (or self-imaging, i.e., first imaging) of the first grating G1 when passing through the second grating G2 is enlarged, and the enlarged second imaging can be observed on the detector.

As an embodiment of the present invention, an interleaving distance between adjacent first grating units or adjacent second grating units is Δ x (i.e., the above-mentioned offset difference), and satisfies the following formula:

wherein a is a positive integer as a constant of the above formula; p is the period of the first grating G1 or the second grating G2, and N is the number of phase steps of the first grating G1 or the second grating G2 during an imaging scan. Specifically, as shown in fig. 11, the second grating G2 is composed of three second grating units G21, G22 and G23 spliced together in a staggered manner in a vertical direction, wherein widths of the second grating units G21, G22 and G23 are respectively x₂₁、x₂₂(not shown), x₂₃. At this time, the misalignment difference Δ x between the second grating units G21, G22₁And a misalignment difference Deltax between the second grating units G22, G23₂The following formula is satisfied:

similarly, the above formula is also applicable to the first grating G1.

As an embodiment of the invention, an imaging illumination bit is arranged between the first grating G1 and the second grating G2. In the grating imaging system in the art, in order to obtain a clearer imaging effect with a smaller imaging magnification, the imaging illumination position is generally arranged between the source grating G0 and the first grating G1. However, such a design would result in about 1/4X-ray total amount received by the detector, which is the total amount of X-ray penetrating the object at the imaging irradiation position, and at the same image quality level, the absorption dose of the detected object would be about 4 times that of the conventional X-ray attenuation imaging (such as X-ray chest radiography imaging, etc.), which is difficult to achieve the clinical radiation dose standard. In order to reduce the radiation dose of the system, as an embodiment of the present invention, the imaging irradiation position is placed between the first grating G1 and the second grating G2 in the elliptical position between the first grating G1 and the second grating G2 as shown in fig. 10, so that the radiation dose of the object is reduced, and the generation of ineffective X-rays is reduced as shown in fig. 1. Compared with the system structure design that an object is placed between the source grating G0 and the first grating G1, the radiation dose of the system structure design is reduced by about half, and the system structure design optimization is easier to achieve clinical standards.

As an embodiment of the invention, the first grating G1 or the second grating G2 is a curved grating or a two-dimensional grating. Specifically, as an embodiment of the present invention, the first grating G1 or the second grating G2 may be a curved grating, and the first grating G1 may be formed by splicing a plurality of first grating units in a staggered manner along a certain curve direction; the second grating G2 is formed by splicing a plurality of second grating units in a staggered manner along the curve direction, and both the first grating G1 and the second grating G2 have a certain radian. In addition, the first grating G1 and the second grating G2 are formed by splicing a plurality of first grating units and a plurality of second grating units along a specific direction in a two-layer manner, that is, the first grating unit includes an upper grating unit and a lower grating unit which are superposed and combined, and the first grating G1 and the second grating G2 are two-dimensional plane gratings.

As an embodiment of the present invention, when the first grating unit is horizontal in the grid direction, a plurality of the first grating units are spliced in a staggered manner in the horizontal direction to form a first grating G1, and a plurality of the second grating units are spliced in a staggered manner in the horizontal direction to form a second grating G2; or when the grid direction of the first grating units is vertical, the first grating units are spliced in a staggered mode along the vertical direction to form a first grating G1, and the second grating units are spliced in a staggered mode along the vertical direction to form a second grating G2.

As an embodiment of the present invention, when the first grating unit is horizontal in the grid direction, a plurality of the first grating units are spliced in a staggered manner in the vertical direction to form a first grating G1, and a plurality of the second grating units are spliced in a staggered manner in the vertical direction to form a second grating G2; or when the grid direction of the first grating units is vertical, the first grating units are spliced in a staggered mode along the horizontal direction to form a first grating G1, and the second grating units are spliced in a staggered mode along the horizontal direction to form a second grating G2.

Specifically, as shown in fig. 10, the 4 first grating units G11, G12, G13, and G14 have horizontal grid directions, and are spliced in a staggered manner in the vertical direction (Z axis) to form the first grating G1, the grid directions of the second grating units of the corresponding second grating G2 are irrelevant thereto, and when the splicing directions are ensured to be opposite, specifically, the splicing directions are either positive or negative along the x axis, and preferably, the grid directions of the 7 second grating units G21, G22, G23, G24, G25, G26, and G27 are horizontal, and are spliced in a staggered manner in the vertical direction (Z axis) to form the second grating G2, that is, when the central connection line between the second grating G2 and the first grating G1 is consistent with the optical path, the splicing direction of the selectable second grating units is consistent with the splicing direction of the first grating units.

In another aspect, the present invention provides a raster imaging scanning method applied to the raster imaging system, as shown in fig. 12, the method includes:

s1210, controlling the system to move along the vertical direction to scan the imaging irradiation position between the first grating G1 and the second grating G2;

s1220, exposing the imaging irradiation position at a specific scanning height;

s1230, extracting the exposed data information to acquire imaging; the first grating G1 comprises a plurality of first grating units which are spliced in a staggered mode, and/or the second grating G2 comprises a plurality of second grating units which are spliced in a staggered mode.

Specifically, as an embodiment of the present invention, the first grating G1, the light source and the source grating G0 are generally moved to perform vertical scanning, and the second grating G2 is moved to perform phase-stepping scanning simultaneously, where the phase-stepping scanning of the second grating G2 is independent of the grid direction of the second grating G2 or the first grating G1, so as to be distinguished from the case where the phase-stepping direction of the second grating G2 changes with the grid direction (for example, the phase-stepping direction and the grid direction of the gratings are perpendicular to each other in the same vertical plane).

As an embodiment of the present invention, exposing the imaging radiation site at a specific scan height includes: wherein, the height difference h between the nth and the n +1 th corresponding first or second grating units of the first or second grating G1 or G2_n,n+1The following formula is satisfied:

h_n,n+1＝m·Δh

wherein m is a positive integer, Δ h is a third distance between the first specific scanning height and the second specific scanning height; when the system moves the first grating G1, the light source and the source grating G0 to perform vertical scanning, a scanning height difference can be set as the third distance, and the imaging irradiation positions are respectively exposed at intervals of the third distance to acquire exposure images, that is, the scanning imaging process is completed.

Specifically, as an embodiment of the present invention, since there may be a gap in the splicing process of the gratings, the height difference may be understood as the gap. The height difference between adjacent two first grating units of the first grating G1 and the height difference between adjacent two second grating units of the second grating G2 may be both applied to the above formula. Specifically, as shown in fig. 11, as an embodiment of the present invention, the second grating G2 is composed of a plurality of second grating units, each of the second grating units is located in a second grating G2 background, the grating direction of the second grating unit is perpendicular to the Z-axis direction, that is, the grating direction of the second grating unit is horizontal, wherein 21 st, 22 th, and 23 th second grating units G21, G22, and G23 are formed by progressively staggered-splicing in the vertical direction, and the heights thereof are respectively h₂₁、h₂₂、h₂₃When n is 21 and n +1 is 22, the height difference h between the 21 st and 22 nd second grating units of the second grating G2 is_21,22The following formula is satisfied:

h_21,22＝m·Δh

where m is a positive integer and Δ h is a third distance between the first specific scanning height and the second specific scanning height.

The above formula represents the height difference between two adjacent second grating units in the second grating units.

Fig. 13 shows the actual experimental result of a sample, wherein the experimental sample is a porcine clavicle, and fig. 13 shows an absorption information image (a), a phase contrast information image (b), and a dark field information image (c) of the sample, respectively: the scale bar of the image is 30mm, the number of phase steps is 9, the distance from the source grating G0 to the first grating G1 is 1657mm, the periods of the source grating G0, the first grating G1 and the second grating G2 are 15.75 μm, 7.00 μm and 12.60 μm respectively, the duty cycles thereof are 0.7, 0.5 and 0.5 respectively, and the areas thereof are 50 × 25mm respectively²、240×50mm²And 400X 80mm²The gold plating thickness of the first grating G1 is 150 μm, 150 μm and 250 μm respectively, the X-ray tube voltage of 75kV and the tube current of 320mA, the single exposure time is 80ms, and the pixel size of the detector is 150 μm. Therefore, the large-area grating imaging system provided by the invention can greatly improve the imaging field of vision, effectively reduce the radiation dose, improve the scanning efficiency and obtain the absorption, phase contrast and dark field image information with better image quality.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A grating imaging system, comprising a source grating (G0), a first grating (G1), and a second grating (G2) arranged in sequence along an optical path, wherein:

a source grating (G0) for converting incoherent light emitted by the light source into coherent light;

a first grating (G1) formed by splicing a plurality of first grating units and used for acquiring a first image after the coherent light passes through the first grating (G1); and

a second grating (G2) formed by splicing a plurality of second grating units and used for operating the first imaging to obtain a second imaging;

wherein an imaging illumination position is arranged between the first grating (G1) and the second grating (G2).

2. The system according to claim 1, wherein when the first and second grating units are respectively spliced along a one-dimensional direction, the first grating (G1) and the second grating (G2) satisfy the following formula:

wherein, w₁Is the width, h, of the first grating (G1)₁Is the height of the first grating (G1); w is a₂Is the width, h, of the second grating (G2)₂Is the height of the second grating (G2); l is a first pitch between the source grating (G0) and the first grating (G1), d is a second pitch between the first grating (G1) and the second grating (G2).

3. The system of claim 2, wherein the second distance d between the first grating (G1) and the second grating (G2) satisfies the following equation:

wherein l is a first spacing between the source grating (G0) and the first grating (G1); p is a radical of₀、p₁、p₂The periods of the source grating (G0), the first grating (G1) and the second grating (G2), respectively, lambda is the X-ray wavelength, n is a constant, n is an odd number when the first grating (G1) is a phase grating, n is an even number when the first grating (G1) is an absorption grating, η is another constant related to the grating type, η is 1 when the first grating (G1) is a pi/2 phase grating or absorption grating, and the first grating (G1) is 2 when the first grating (G1) is a pi phase grating.

4. The system according to claim 3, wherein when the first grating (G1) is an absorption grating, a second pitch d between the first grating (G1) and the second grating (G2) satisfies the following equation:

wherein l is a first spacing between the source grating (G0) and the first grating (G1); p0, p1, p2 are the periods of the source grating (G0), the first grating (G1) and the second grating (G2), respectively.

5. The system of claim 1,

when the first grating unit is horizontal in the grating direction, a plurality of first grating units are spliced in the horizontal direction to form a first grating (G1), and a plurality of second grating units are spliced in the horizontal direction to form a second grating (G2); or

When the first grating units are vertical in the grating direction, a plurality of the first grating units are spliced along the vertical direction to form a first grating (G1), and a plurality of the second grating units are spliced along the vertical direction to form a second grating (G2).

6. The system of claim 1,

when the grid direction of the first grating units is horizontal, a plurality of the first grating units are spliced along the vertical direction to form a first grating (G1), and a plurality of the second grating units are spliced along the vertical direction to form a second grating (G2); or

When the first grating units are vertical in the grating direction, the first gratings (G1) are formed by splicing a plurality of the first grating units along the horizontal direction, and the second gratings (G2) are formed by splicing a plurality of the second grating units along the horizontal direction.

7. The system of claim 1, further comprising a detector having a pixel size larger than a period of the first grating (G1) for viewing a second image of the second grating (G2).

8. The system according to claim 1, wherein the first grating (G1) is provided with a metallized layer thereon, the material of the metallized layer being selected as a heavy element metal, comprising: gold, silver, tungsten or lead.

9. The system according to claim 1, wherein a plurality of the first grating units and a plurality of the second grating units are respectively spliced in a laminated manner along a one-dimensional direction to form the first grating (G1) and the second grating (G2), and the first grating (G1) and the second grating (G2) are two-dimensional plane gratings.

10. The system according to claim 9, wherein, when said stack is a double stack, the grid shape of said two-dimensional planar first grating (G1) is defined by the grating periods p of the first and second stacked grating elements of said first grating element₁₁、p₁₂And its grid direction; and

the two-dimensional planar second grating (G2) has a grating period p defined by the grating periods of the third and fourth stacked grating elements of the second grating element₂₁、p₂₂And its grid direction.

11. A raster imaging scanning method applied to the raster imaging system according to any one of claims 1 to 10, characterized in that the method comprises:

controlling the system to move in a vertical direction to scan an imaging illumination location between a first grating (G1) and a second grating (G2);

exposing the imaging illumination location at a particular scan height;

and extracting the exposed data information to acquire imaging.

12. The method of claim 11, wherein exposing the imaging illumination bits at a particular scan height comprises:

exposing the imaging exposure location when the system reaches a specified scan height and then controlling the second grating (G2) to perform a phase step scan in the horizontal direction for a specified scan step length.

13. The method of claim 11, wherein exposing the imaging illumination bits at a particular scan height comprises:

controlling the second grating (G2) to perform a phase-stepping scan in the horizontal direction to a specific scan step size before the system reaches a specific scan height; and

exposing the imaging exposure site after the system reaches a particular scan height.

14. The method of claim 11, wherein exposing the imaging illumination bits at a particular scan height comprises:

completing the first exposure at a first specific scanning height, and completing the second exposure at a second specific scanning height;

wherein the height difference h between the nth and the (n + 1) th first grating units of the first grating (G1)_n,n+1The following formula is satisfied:

h_n,n+1＝m·Δh

wherein m is a positive integer, Δ h is a third distance between the first specific scanning height and the second specific scanning height;

a height difference h between the nth and the n +1 th second grating units of the second grating (G2)_n,n+1The following formula is satisfied:

where m is a positive integer, l is a first spacing between the source gratings (G0) and (G1), and p₂Is the period of the second grating (G2), N is the number of phase steps of the second grating (G2).